Electrosurgical hemostatic device

ABSTRACT

An improved electro surgical instrument is provided for cauterization and/or welding of tissue of varying impedances, thicknesses and vascularity especially in the performance of endoscopic procedures. The instrument compresses the tissue between one pole of a bipolar energy source located on one interfacing surface, and a second interfacing surface. A second pole is located on one of the two interfacing surfaces. In a preferred embodiment, the second pole is located on the same interfacing surface as the first pole and an insulator electrically isolates the two poles. A preferred application of the invention is in a cutting instrument wherein a hemostatic line is formed along a cut line using RF energy.

This is a continuation-in-part of application Ser. No. 08/825,842 filedApr. 14, 1997, which is a continuation of application Ser. No.08/385,931 filed Feb. 3, 1995, now abandoned, which is a continuation ofSer. No. 08/095,797, now U.S. Pat. No. 5,403,312 filed Jul. 22, 1993.

FIELD OF THE INVENTION

This invention relates to an improved electro surgical instrument forcauterization, coagulation and/or tissue welding in the performance ofsurgical procedures, especially endoscopic procedures.

BACKGROUND OF THE INVENTION

Surgical procedures requiring cutting of tissue can cause bleeding atthe site of the cutting. Before surgeons had the means to controlbleeding many surgical procedures were quite difficult to performbecause of excessive blood loss. Hemostasis is even more crucial inendoscopic or laparoscopic surgery where if the bleeding is not keptunder control, the laparoscopy must be abandoned and the patient's bodycut to perform open surgery so that inaccessible bleeding may becontrolled.

Thus, various techniques have been adapted to control bleeding withvarying degrees of success such as, for example, suturing, applyingclips to blood vessels, and stapling, as well as electrocautery andother thermogenic techniques. Advances in tissue joining, tissue repairand wound closure also have permitted surgical procedures previously notpossible or too risky.

Initially, suturing was one of the primary means for providinghemostasis and joining tissue. Before other hemostatic and tissue repairmeans were introduced, surgeons had to spend a great deal of time sewingthe tissue of patients back together.

Surgical clips were introduced as a means to close off blood vessels,particularly when cutting highly vascularized tissue. Application ofsurgical clips, however, can be cumbersome in certain procedures. Thevessels must be identified. Then a clip must be individually applied onboth sides of the intended cut of each identified vessel. Also, it maybe difficult to find some vessels, particularly where the vessel issurrounded by fatty tissue.

Surgical staplers have been effective in decreasing the amount of timeit takes to fasten tissue together. There are various types of surgicalstaplers. Staplers have been used for tissue joining, and to providehemostasis in conjunction with tissue cutting. Such devices include, forexample, linear and circular cutting and stapling instruments.Typically, a linear cutter has parallel rows of staples with a slot fora cutting means to travel between the rows of staples. This type ofsurgical stapler secures tissue for improved cutting, joins layers oftissue, and provides hemostasis by applying parallel rows of staples tolayers of surrounding tissue as the cutting means cuts between theparallel rows. These types of cutting and stapling devices have beenused successfully in procedures involving fleshy tissue such as muscleor bowel, particularly in bowel resection procedures. Circular cuttingand stapling devices have successfully been used, for example, inanastomotic procedures where a lumen is rejoined. However, the resultswith cutting and stapling devices have been less than optimum where theprocedure involves cutting highly vascularized tissue, such as mesenteryor adnexa, which are prone to having hemostasis problems.

Electrocautery devices have also been used for effecting hemostasis.Monopolar devices utilize one electrode associated with a cutting orcauterizing instrument and a remote return electrode, usually adheredexternally to the patient. More recently, bipolar instruments have beenused because the cauterizing current is generally limited to tissuebetween two electrodes of the instrument.

Bipolar forceps have been used for cutting and/or coagulation in variousprocedures. For example, bipolar forceps have been used in sterilizationprocedures where the fallopian tubes are sealed off. Generally, bipolarforceps grasp tissue between two poles and apply electrical currentthrough the grasped tissue. Bipolar forceps, however, have certaindrawbacks, some of which include the tendency of the current to arcbetween poles when tissue is thin or the forceps to short when the polesof the forceps touch. The use of forceps for coagulation is also verytechnique dependent and the forceps are not adapted to simultaneouslycauterize a larger area of tissue.

Bipolar scissors have been disclosed where two scissors blades act astwo electrodes having insulated shearing surfaces. This devicemechanically cuts tissue as coagulating electrical current is deliveredto tissue in the current path. Bipolar scissors are also highlytechnique dependent in their use.

In prior devices, electro surgical energy has been delivered to biologictissue in order to create a region of coagulation, as, for example, oneither side of an incision, thus preventing blood and other bodilyfluids from leaking out of the incision. In prior art devices, thesurgeon has used tactile feedback and visual clues to determine when thetissue is properly coagulated. Alternatively, electrical feedback ortiming circuits may be used to determine when coagulation is complete.In electro surgical devices wherein the coagulation region is partiallyor fully obscured by the jaws of the end effector, it may be difficultfor the surgeon to judge the degree of coagulation in order to turn offthe bipolar energy or to ensure that the degree of hemostasis issufficient prior to cutting. In devices where feed back or timing isused to calculate the degree of coagulation, it is desirable to ensurethat the instrument is treating the tissue evenly and predictably. Itwould, therefore, be advantageous to develop an improved electrosurgical instrument wherein the arrangement of the electrodes,compression ridges and insulation regions have been optimized to enhancetissue coagulation.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide ahemostatic electro surgical instrument which can efficiently providehemostasis in multiple tissue types and thickness, e.g., in fleshy orvascular tissue areas, and high, low or combination impedance tissues.Hemostasis is used herein to mean generally the arresting of bleedingincluding by coagulation, cauterization and/or tissue joining orwelding.

It is another object of the invention to provide a bipolar hemostaticdevice which is capable of being used to simultaneously cauterize orweld a relatively larger area or length of tissue than in previouslyknown devices.

It is another object of the invention to provide a bipolarelectrocautery device having elongated or bar electrodes.

Another object of the invention to is provide a hemostatic means forproviding a line of coagulation adjacent to a cutting path of a cuttingmeans for dividing tissue.

Another object of the invention is to provide a cutting and staplingdevice with an electrocautery means for tissue welding or cauterizationalong a cutting path.

These and other objects of the invention are described in an electrosurgical device having an end effector with opposing interfacingsurfaces associated with jaws for engaging tissue therebetween, and twoelectrically opposite poles located on one or both of the opposingsurfaces. The poles are isolated from each other with an insulatingmaterial, or, where the poles are on opposite interfacing surfaces, theyare offset from each other so that they are not diametrically opposedfrom each other on interfacing surfaces.

An electrosurgical instrument of a preferred embodiment compressestissue in a compression zone between a first interfacing surface and asecond interfacing surface and applies electrical energy through thecompression zone. The first interfacing surface is comprised of: a firstpole of a bipolar energy source, which interfaces with the compressedtissue in the compression zone; and a second pole electrically isolatedfrom the first pole and located on the same or opposite interfacingsurface. Electrically isolated poles are defined herein to meanelectrodes isolated from each other by an insulating material in the endeffector and/or offset from each other on opposing surfaces.

In a preferred embodiment, the compression zone is an area defined by acompression ridge on one of the interfacing surfaces which compressesthe tissue against the other interfacing surface. Also, there may be acompression ridge on both interfacing surfaces. A coagulation zone isdefined by the first pole, the second pole, and an insulator insulatingthe first pole from the second pole. The second pole, located on one ofthe interfacing surfaces, is generally adjacent to the insulator on thesame interfacing surface or across from the insulator on an opposingsurface. This arrangement electrically isolates the two poles andenables the current path between the first and second poles to crossthrough a desired area of tissue.

It is believed that the tissue compression normalizes tissue impedanceby reducing structural differences in tissue which can cause impedancedifferences. Compression also stops significant blood flow and squeezesout blood which acts as a heat sink, particularly when flowing throughblood vessels. Thus, compression optimizes delivery of energy to tissuein part by enabling the rate of energy delivery to exceed the rate ofdissipation due to blood flow. The arrangement of the electrodes, whichmake up the poles, is important to ensure that the current passingbetween the two poles passes though the compression zone. Also,insulation or isolation of the opposite poles from each other on theinstrument permits tissue compression without shorting of the instrumentpoles or electrical arcing common in bipolar instruments.

In one embodiment of an electro surgical device according to the presentinvention, the first electrically isolated pole includes first andsecond electrodes form a first compression ridge positioned on a firstsurface of the first jaw on either side of a knife channel. In thisembodiment of the invention, the tissue contacting surfaces of the firstelectrodes are approximately 0.02 inches to approximately 0.04 inches.The portion of the second jaw opposite the first electrically isolatedpole is an insulator which forms a second compression ridge. The firstjaw further includes a first recessed insulation region having a widthof between approximately 0.01 to approximately 0.04 inches and which isrecessed from the tissue contacting portion of the first electricallyisolated pole and positioned on the surface of the first jaw outside ofthe first isolated pole. The second jaw also may include a secondrecessed insulation region opposite the first recessed insulationregion. The second stepped region may have a width approximately equalto the width of the first stepped region. The first jaw may also includethe second electrically isolated pole in a position outside of the firstrecessed insulator such that the distance from the tissue contactingportion of the first stepped electrode to the tissue contacting surfaceof the second electrode is in the range of between approximately 0.001inches to approximately 0.045 inches.

Thus, the tissue compression and the arrangement of the electrodespermit more efficient cauterization and offer the advantage of achievinghemostasis in a wide range of tissue impedance, thickness andvascularity.

Compression is preferably balanced against causing unacceptable tissuedamage from excessive compression. A gap between jaws can be varieddepending on the intended application of instrument or the thicknessesof tissue on which the instrument is used.

In an alternative embodiment of the invention, the first pole is locatedon a first interfacing surface of a first jaw and the second pole islocated on the same jaw as the first pole, but not on the interfacingsurface.

The present invention also provides a device capable of coagulating aline or path of tissue along or lateral to a cut line or a cutting path.In one embodiment, the first pole comprises an elongated electrode. Theelongated electrode along with the adjacent insulator form a ridge tocompress the tissue to be cauterized. The second pole is adjacent theinsulator on an opposite side of the insulator from the first pole.

In one preferred embodiment, a cutting means for cutting tissue isincorporated into the device and the device provides hemostatic linesadjacent to the path of the cutting means. Of course, cutting may occurat anytime either before, during or after cauterization or welding. Inone variation of this preferred embodiment, stapling means is providedon one or both sides of the cutting path.

In one embodiment, an indicator means communicates to the user that thetissue has been cauterized to a desired or predetermined degree.

In another embodiment, the coagulation is completed prior to anymechanical cutting, i.e., actuation of the cutting means. If anindicator means is used, once tissue is cauterized, the cutting meansmay be actuated to cut between the parallel bars while the rows ofstaples are applied to the tissue.

In another embodiment, the hemostatic device is incorporated into alinear cutter similar to a linear cutting mechanical stapler. In thisembodiment the hemostatic device comprises two parallel and joinedelongated electrode bars which form one pole, and a slot for a cuttingmeans to travel between the bars. Optionally, one or more rows ofstaples may be provided on each side of the slot and bars to provideadditional hemostasis. In operation, tissue is clamped between two jaws.Electrical energy in the form of radio frequency current is applied tothe compressed tissue to cauterize the blood vessels along the twoparallel bars.

Another embodiment provides a means for detecting abnormal impedances orother electrical parameters which are out of a predetermined range. Forexample, the means for detecting may be used to indicate when theinstrument has been applied to tissue exhibiting impedances out of rangefor anticipated good coagulation. It may also be used for detectingother instrument abnormalities. It is possible to detect the abnormalcondition, for example, by using comparisons of normal ranges of initialtissue impedances in the interface electronics. This could be sensed inthe first few milliseconds of the application of RF energy and would notpresent a significant therapeutic dose of energy. A warning mechanismmay be used to warn the user when the impedance is out of range. Uponrepositioning of the instrument, the same measurement criteria wouldapply and if the tissue impedance was again out of range, the user wouldagain be warned. This process would continue until the normal impedancerange was satisfied and good coagulation could be anticipated.

Similarly another embodiment provides a tissue welding and cauterizingcutting device similar to an intraluminal stapler. Preferably, the polesare formed in two concentric circle electrodes separated by aninsulator. The electrodes which make up the poles may be located oneither the stapler cartridge or the anvil.

These and other objects of the invention will be better understood fromthe following attached Detailed Description of the Drawings, when takenin conjunction with the Detailed Description of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of an endoscopic electrocautery linearstapling and cutting instrument of one embodiment of the presentinvention;

FIG. 2 is a side cross sectional view of the instrument of FIG. 1;

FIG. 3 is a partial cross sectional view of the distal end of theinstrument of FIG. 1 in an open position;

FIG. 4 is a partial cross sectional view of the distal end of theinstrument of FIG. 1 in a closed, unfired position;

FIG. 5 is a partial cross sectional view of the distal end of theinstrument of FIG. 1 in a closed, fired position;

FIG. 6 is a front cross sectional view of the distal end of theinstrument of FIG. 3 taken along the line 6--6;

FIG. 7 is a bottom isolated view of the anvil jaw of the instrument ofFIG. 1;

FIG. 8 is a top isolated view of a cartridge of the instrument of FIG.1;

FIG. 9 is a side cross sectional view of the jaw of FIG. 7 along theline 9--9;

FIG. 10 is a flow chart illustrating a feedback system of the presentinvention;

FIG. 11 is a front cross sectional view of the end effector of anotherembodiment of the present invention;

FIG. 12 is a front cross sectional view of the end effector of anotherembodiment of the present invention;

FIG. 13 is a front cross sectional view of the end effector of anotherembodiment of the present invention;

FIG. 14 is a front cross sectional view of the end effector of anotherembodiment of the present invention;

FIG. 15 is a bottom isolated view of the anvil of another embodiment ofthe present invention;

FIG. 16 is a bottom isolated view of the anvil of another embodiment ofthe present invention;

FIG. 17 illustrates a cross sectional view of the distal end of anotherembodiment of the present invention;

FIG. 18 is front cross sectional view of the end effector of FIG. 17;

FIG. 19 is a front cross sectional view of the end effector of anotherembodiment of the present invention;

FIG. 20 is a top view of a cartridge of a circular cutter of the presentinvention;

FIG. 21 is a bottom view of the anvil of a circular cutter of thepresent invention.

FIG. 22 is a cross sectional view of the end effector according to afurther embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1-9, there is illustrated a preferred embodimentof the present invention. An endoscopic electrocautery linear cuttingand stapling instrument 10 is shown having a body 16 coupled to a shaft30 with a lumen extending therethrough and an end effector 50 extendingfrom the distal end 21 of the shaft 30. The shaft 30 is formed of aninsulative material and has an electrically conductive sheath 38extending through its lumen. A channel 39 extending through the sheath38 guides co-axial movement of a driver means 44 within the channel 39.In this particular embodiment, the driver means 44 includes a firingtrigger 14 associated with the body 16, coupled to a flexible firing rod40 coupled to a driving rod 41, coupled to a block 43. The block 43 iscoupled to a cutting means 11 and a staple driving wedge 13, which thedriving means 44 advances by way of the block 43 into the end effector50.

The end effector 50 comprises two interfacing jaw members 32, 34. Theend effector 50 is secured by way of jaw member 34 to the channel 39.The jaw member 32 is movably secured to jaw member 34. The body 16 has aclamping trigger 12 for closing the jaws 32, 34 which longitudinallyadvances a close rack 45 coupled to the proximal end of the sheath 38.The close rack 45 advances the sheath 38 co-axially through the shaft30. The sheath 38 advances over a camming surface 27 of jaw 32 to closethe jaws 32 and 34 onto tissue situated between the jaws. As describedin more detail below, the close rack 45 also acts as a switch to closethe circuit which communicates electrical energy to the end effector 50.

Referring now to FIGS. 3-9 and 22 an enlargement of the end effector 50of the instrument 10 is illustrated. The jaw members 32 and 34 are shownin an unclamped position in FIG. 3, in a clamped, unfired position inFIG. 4 and in a clamped, fired position in FIG. 5. Jaw member 32comprises an anvil 18, a U-shaped first pole 52 extending longitudinallywith respect to the jaw 32, and a U-shaped insulating material 55surrounding the outside of the first pole 52. Jaw member 32 has an innersurface 33 which faces an inner surface 35 of jaw 34. The inner surface33 includes first pole 52 which comprises two electrically communicatingelectrode bars 53, 54 comprised of stainless steel or aluminum,extending substantially along the length of the inner surface 33. Thebars 53, 54 are separated by a knife channel 42 extending longitudinallythrough the first pole's center to form its U-shape. The surface of thebars are formed in flat strips to provide more surface area contact withtissue. Two series of pockets 36, 37 located on anvil 18, for receivingstaple ends, extend along the inner surface 33, lateral to and outsideof bars 53, 54 respectively. The electrode bars 53, 54 and theinsulating material 55 form a ridge 56 extending out relative to theanvil portion 33a of the inner surface 33 (FIG. 6). The anvil 18 isformed of an electrically conductive material and acts as a second pole18a electrically opposite to the first pole. The anvil 18 is isolatedfrom the first pole 52 by the U-shaped insulating material 55.

Jaw member 34 comprises a cartridge channel 22 and a cartridge 23. Thecartridge 23 includes a track 25 for the wedge 13, knife channel 26extending longitudinally through the center of the cartridge 23, aseries of drivers 24 extending into track 25 and staples 100 arranged intwo sets of parallel double rows. When tissue is engaged between thejaws 32, 34, the driver means 44 may be actuated or fired using trigger14 to advance the cutting means 11 and wedge 13 through the engagedtissue to staple and cut the tissue. When the firing mechanism 14 isactuated, the wedge 13 is advanced through the track 25 causing thedrivers 24 to displace towards the staples 100, thereby driving thestaples 100 through tissue and into anvil pockets 36, 37.

In the embodiment of the invention illustrated in FIG. 22, Dimension B,which is measured from the anvil portion 33a of the inner surface 33 ofjaw member 32 to the tissue contacting surface 80 of U-shaped insulatingmaterial 55, is preferably in the range of from approximately 0.0 inchesto approximately 0.045 inches and preferably approximately 0.0 inches.In the embodiment illustrated in FIG. 22, U-shaped shaped insulatingmaterial 55 separates first pole 52 from second pole 18a. As illustratedin FIG. 22, Dimension C is measured from inner edge 82 to outer edge 84of U-shaped insulating material 55 along tissue contacting surface 80.In one embodiment of the present invention, Dimension C is preferably inthe range of from approximately 0.01 inches to approximately 0.04 inchesand preferably approximately 0.02 inches. As illustrated in FIG. 22,Dimension E is measured from inner edge 88 to outer edge 86 of firstpole 52 along tissue contacting surface 90. In one embodiment of thepresent invention, Dimension E is in the range of from approximately0.002 inches to 0.04 inches and preferably approximately 0.020 inches.As illustrated in FIG. 22, Dimension G is measured from tissue surface90 to tissue surface 92 with jaws 32 and 34 closed (without tissueengaged). In one embodiment of the present invention, Dimension G ispreferably in the range from approximately 0.0 inches to approximately0.020 inches and preferably approximately 0.001 inches.

In the present invention, the electrodes may be constructed of, forexample, stainless steel (301), solder, aluminum, copper, gold or brass(in pure form or as alloys). In addition, the electrode may be formed byplating or depositing the electrode material. Further, in the presentinvention, the anvil may be constructed of, for example, stainless steel(17-4), aluminum or ceramic. The insulation material may be, forexample, Nylon, PPO (Noryl), urethane, polycarb, PEI, PTFE (Teflon) orceramic material. Finally, the cartridge material may be, for example,Vectra, Noryl, Polycarb, ABS or a urethane material.

A knob 15 located on the distal end of the body 16 rotates the shaft 30,sheath 38, channel 39 and end effector 50 which are directly orindirectly coupled to the knob 15 so that the knob 15 may be used forrotational placement of the end effector jaws 32,34.

Bipolar energy is supplied to the end effector 50 from an electrosurgical generator 60 through wires 19, 20 extending into the body 16 ofthe instrument. The generator 60 is user controlled by way of afootswitch 65.

Wire 19 which provides electrical current to the first pole, is coupledthrough a wire or other electrical contact means 61 to electricalcontact 62, associated with the first pole, located on the distal end ofclose rack 45. Wire 20 which carries the current of the opposite pole,is coupled through a wire or other electrical contact means 66 to a disccontact 67 located at the distal end of the close rack 45 andelectrically isolated from contact 62.

A disc contact 63, associated with the first pole, located at the distalend of the body 16 is in electrical communication with a wire or othercontact means 64. Contact means 64 extends through channel 39 to endeffector jaw 32 where it contacts first pole 52. The disc contact 63permits the knob 15 to rotate while contact is maintained between thedisc contact 63 and the contact means 64. The contact means 64 iselectrically insulated from the sheath 38.

When the clamping trigger 12 is actuated, the close rack 45 movesdistally so that the contact 62 comes in electrical communication withthe disc contact 63 and the disc contact 67, associated with the secondpole 51, comes in electrical contact with the electrically conductivesheath 38. The sheath 38 moves over the camming surface 27 of theelectrically conductive anvil 18 which acts as the return electrode.Thus the electrical circuit is closed when and only when the clampingtrigger 12 is closed.

In operation, the end effector 50 of the instrument is located at atissue site where tissue is to be cut. The jaw members 32, 34 are openedby pressing a release button 70 which releases a button spring 71 andpermits the close rack 45 to move proximally. Tissue is then placedbetween the interfacing inner surfaces 33, 35 respectively of the jawmembers 32, 34. The clamping trigger 12 is squeezed to cause the sheath38 to move over the camming surface 27 and thereby close the jaws 32, 34and simultaneously close the electrical circuit as described above. Theelectrode bars 53, 54 and the insulating material 55, which togetherform the ridge 56, compress the tissue against the inner surface 35 ofjaw member 34. A user then applies RF energy from the generator 60 usingthe footswitch 65 or other switch. Current flows through the compressedtissue between the first pole 52, i.e. the bars 53, 54, and the secondpole 51, i.e., the anvil 18.

Preferably the bipolar energy source is a low impedance source providingradio frequency energy from about 300 kHz to 3 MHZ. Preferably, thecurrent delivered to the tissue is from 0.1 to 1.5 amps and the voltageis from 30 to 200 volts RMS.

An audible, visible, tactile, or other feedback system may be used toindicate when sufficient cauterization has occurred at which point theRF energy may be turned off. An example of such a feedback system isdescribed below. After the RF energy is turned off, the cutting means 11is advanced and the staples 100 are fired using the firing trigger 14.Firing is accomplished by rotating the firing trigger 14 acting as alever arm about pivot 14a. The driver means 44 advances the cuttingmeans 11 and wedge 13. The cutting means 11 cuts the tissue in betweenthe bars 53, 54 where the tissue has been cauterized. Thus, the cut lineis lateral to the coagulation lines formed by the bar electrodes. Thewedge 13 simultaneously advances the drivers 24 into the staples 100causing the staples 100 to fire through tissue and into the pockets 36,37 of the anvil 18. Staples 100 are applied in two longitudinal doublerows on each side of the cutting means 11 as the cutting means cuts thetissue.

Operation of linear staplers are known in the art and are discussed, forexample, in U.S. Pat. Nos. 4,608,981, 4,633,874, and U.S. Pat. No.5,367,976 incorporated herein by reference.

In one embodiment the cartridge provides multifire stapling capabilitiesby replacing the double row of staples with a single row. In thelaparoscopic stapling and cutting devices presently in use, a singleshot replaceable cartridge is used. In order to provide betterhemostasis, this type of stapler was designed to provide a double row ofstaples for each parallel row. Because of the size of the spacenecessary to contain the double row of staples, a refireable cartridgewith stacked staples has not been preferred because of the additionalspace required for stacking staples. In the multifire staplingembodiment a single row of staples is used. Using a single row ofstaples permits stacking of staples in the space previously occupied bythe second row of staples, providing multifire capabilities. In afurther embodiment, no staples are required and the electrical currentlines provide the necessary hemostasis.

A preferred embodiment of the present invention includes a feedbacksystem designed to indicate when a desired or predetermined degree ofcoagulation has occurred. This is particularly useful where thecoagulation zone is not visible to the user. In a particular embodiment,the feedback system measures electrical parameters of the system whichinclude coagulation level.

The feedback system may also determine tissue characteristics at or neara coagulation zone which indicate degree of coagulation. The electricalimpedance of the tissue to which the electrical energy is applied mayalso be used to indicate coagulation. Generally, as energy is applied tothe tissue, the impedance will initially decrease and then rise ascoagulation occurs. An example of the relationship between electricaltissue impedance over time and coagulation is described in Vaellfors,Bertil and Bergdahl, Bjoern "Automatically controlled BipolarElectrocoagulation," Neurosurg. Rev. p. 187-190 (1984) incorporatedherein by reference. Also as desiccation occurs, impedance increases.Tissue carbonization and or sticking to instrument as a result of overapplication of high voltage may be prevented using a feedback systembased on tissue impedance characteristics. Other examples of tissuecharacteristics which may indicate coagulation include temperature andlight reflectance.

Referring to FIG. 10, a flow chart illustrates a feedback system whichis implemented in a preferred embodiment of the present invention.First, energy is applied to the tissue. Then the system current andvoltage applied to the tissue is determined. The impedance value iscalculated and stored. Based on a function of the impedance, forexample, which may include the impedance, the change in impedance,and/or the rate of change in impedance, it is determined whether desiredcoagulation has occurred. If coagulation has occurred to a predeterminedor desired degree, an indication means indicates that the energy shouldbe turned off. Such an indication means may include a visible light, anaudible sound or a tactile indicator. The feedback means may alsocontrol the generator and turn the energy off at a certain impedancelevel. An alternative embodiment provides a continuous audible sound inwhich the tone varies depending on the impedance level. An additionalfeature provides an error indication means for indicating an error orinstrument malfunction when the impedance is below a normal minimumand/or above a maximum range.

FIGS. 11-14 illustrate alternative configurations of an end effector. InFIG. 11 the first pole 152 and the second pole 151 are both located onthe same jaw 132 having the anvil 118. The U-shaped first pole 152 formsthe knife channel 142. A U-shaped insulator 155 surrounds the first pole152 except on the surface 133 so that it is electrically isolated fromthe second pole 151. The compression ridge 156 is formed on thecartridge which is made from an electrically non-conductive material.The ridge 156 compresses tissue against the first pole 152 and insulator155 to form a tissue compression zone.

In FIG. 12, the first pole 252 and the second pole 251 are both locatedon the same jaw 232 having the anvil 218. The first pole 252 and thesecond pole 251 each are located on opposing sides of the knife channel242. An insulator 255 surrounds the poles 251, 252 except on the surface233 so that the poles 251, 252 are electrically isolated from eachother. The compression ridge 256 is formed on the cartridge which ismade from an electrically non-conductive material. The ridge 256compresses tissue against the poles 251, 252 and insulator 255 to form atissue compression zone.

In FIG. 13, second pole 351 is located on the jaw 332 having the anvil318 while the first pole 352 is located on the cartridge 323. TheU-shaped first pole 352 forms the knife channel 326 and is surrounded byinsulator 355a. A U-shaped insulator 355b forms the knife channel 342 injaw 332. Except for the insulator 355b, the jaw is formed of anelectrically conductive material which makes up the second pole 351. Thefirst pole 352 and the insulator 355a form the compression ridge 356which compresses tissue against the surface 333 of jaw 332 to form acompression zone. The insulator 355b is of sufficient width that itprevents poles 351, 352 form contacting when the jaws 332, 334 areclosed.

In FIG. 14, the first pole 452 and the second pole 451 are both locatedon the jaw 434 having the cartridge 423. The first pole 452 and thesecond pole 451 each are located on opposing sides, forming the knifechannel 426 through the cartridge 423.

An insulator 455a surrounds the poles 451, 452 except on the surface435, so that the poles 451, 452 are electrically isolated from eachother. The compression ridge 456 is formed on the cartridge 423 andforms a compression zone by compressing tissue against an insulator 455bdisposed on the surface 433 of the jaw 432.

FIG. 15 illustrates an alternative embodiment. The first and secondpoles 551, 552 and knife channel 542 are arranged in a similarconfiguration as in FIG. 12 except that the first and second poles 551and 552 each comprise a series of electrically connected electrodesstaggered along the length of the knife channel with insulating materialin between staggered electrodes.

FIG. 16 illustrates staggered electrodes as in FIG. 15 but with firstpole electrodes 652 and second pole electrodes 651 alternating along thelength of the knife channel 642 and on each side of the knife channel642.

FIGS. 17 and 18 illustrate another embodiment in which first and secondpoles 751, 752 each comprise staggered electrodes. In this embodiment,the first pole 752 is staggered along each side of the knife channel 126and located on the compression ridge 756 formed on the cartridge 723.The second pole 751 is staggered along each side of the knife channel742 on the surface 733 of jaw 732. As can be seen from FIG. 18, thepoles 751, 752 are vertically aligned, but as illustrated in FIG. 17,are staggered so that when the jaws 732, 734 are closed, the poles areelectrically isolated from each other by insulators 755a, 755b.

FIG. 19 illustrates an alternative embodiment of the end effector. Thefirst pole 852 and the second pole 851 are both located on the jaw 832having an anvil 818. The first pole 852 forms the ridge 856 forcompressing tissue in a compression zone and is located on interfacingsurface 833. The second pole 851 is located on the side of the anvil 818and not on interfacing surface 833.

FIGS. 20 and 21 illustrate a circular cutter of the present inventionwith stapling means. FIG. 20 illustrates the stapler cartridge 900 withan interfacing surface 933. A double row of staple apertures 901 throughwhich staples are driven into tissue are staggered about the outercircumference of the surface 932. A first pole 952 encircles the innercircumference of the surface 933. An insulator 955 electrically isolatesthe first pole 952 from the portion 933a of the surface 933 surroundingthe staple apertures. The staple aperture portion 933a is formed of anelectrically conductive material and acts as a second pole. A circularcutting knife 911 is recessed within the cartridge 900 radially inwardfrom the inner circumference of the surface 933.

FIG. 21 illustrates an anvil 918 with pockets 937 for receiving staplesand a compression ridge 956 for compressing tissue against the firstpole 952 and insulator 955 of the cartridge. The circular cutter isoperated similarly to the circular stapler described in U.S. Pat. No.5,104,025 incorporated herein by reference. Prior to stapling andcutting however, tissue welding electrical current may be deliveredbetween the first pole 952 and the staple aperture portion 933a totissue.

In an alternative embodiment, the circular cutter may be used withoutstaples. Electrical current is delivered through the poles to weld andcoagulate tissue, then the knife may be advanced to cut tissue in aprocedure such as an anastomosis.

In operation, the jaws of the instrument, for example, jaws 32 and 34 ofend effector 50, are closed around the tissue which is to be treated.Tissue trapped between the instrument jaws is compressed as describedherein

Several variations of this invention has been described in connectionwith two specific embodiments involving endoscopic cutting and stapling.Naturally, the invention may be used in numerous applications wherehemostasis in desired. Accordingly, will be understood by those skilledin the art that various changes and modifications may be made in theinvention without departing from its scope, which is defined by thefollowing claims and their equivalents.

What is claimed is:
 1. An electrosurgical instrument having an endeffector, wherein said end effector comprises:first and second opposinginterfacing surfaces, said interfacing surfaces capable of engagingtissue therebetween, and said end effector capable of receiving bipolarenergy therein; a cutting element arranged on said instrument to cuttissue engaged by said end effector when said cutting element isactuated, wherein said first interfacing surface includes a first slotextending longitudinally therethrough for receiving said cuttingelement; a cartridge containing at least one row of staples and at leastone driver adapted to apply said staples to tissue engaged by said endeffector, said cartridge having a second slot extending longitudinallytherethrough for receiving said cutting element, said first and secondslots arranged to permit said cutting element to travel lateral to saidat least one row of staples, said cartridge forming at least a portionof said second interfacing surface; an anvil for receiving and formingsaid staples, said anvil forming at least a portion of said firstinterfacing surface; electrically isolated first and second polespositioned on said first interfacing surface and comprising electricallyopposite electrodes, wherein said first pole is comprised of first andsecond elongated substantially parallel electrodes arranged on oppositesides of said first slot and said second pole comprises an electrodepositioned on said anvil; first and second compression ridges extendingfrom said first interfacing surface, wherein said first and secondelectrodes comprise at least a portion of said first and secondcompression ridges; third and fourth electrically insulating compressionridges extending from said second interfacing surface; a first tissuecontacting surface on said first and second compression ridges whereinsaid first tissue contacting surface has a width of approximately 0.020inches; a second tissue contacting surface on said third and fourthcompression ridges wherein said second tissue contacting surface has awidth of approximately 0.020 inches; and a recessed insulation regionseparating said first pole from said second pole wherein said recessedinsulation region includes a recessed tissue contacting surface having awidth of approximately 0.020 inches, said recessed tissue contactingsurface being approximately level with said portion of said firstinterfacing surface comprising said anvil.
 2. The electro surgicaldevice of claim 1 wherein said first and second electrodes comprise aseries of electrically communicating electrode regions staggered on saidfirst interfacing surface.
 3. The electrosurgical device of claim 1wherein said one or more first electrodes comprises an electrode havinga relatively circular shape and is located on an outer circumference ofsaid first interfacing surface; andwherein said cutting line is locatedradially inward from said relatively circular electrode.
 4. Anelectrosurgical instrument comprising:a handle, an actuating meanscoupled to said handle, an end effector coupled to the distal end ofsaid actuating means, a means for communicating bipolar electricalenergy from a bipolar energy source to said end effector, said endeffector comprising:first and second opposing interfacing surfaces, saidinterfacing surfaces capable of engaging tissue therebetween, and saidend effector capable of receiving bipolar energy therein; a cuttingelement arranged on said instrument to cut tissue engaged by said endeffector when said cutting element is actuated, wherein said firstinterfacing surface includes a first slot extending longitudinallytherethrough for receiving said cutting element; a cartridge containingat least one row of staples and at least one driver adapted to applysaid staples to tissue engaged by said end effector, said cartridgehaving a second slot extending longitudinally therethrough for receivingsaid cutting element, said first and second slots arranged to permitsaid cutting element to travel lateral to said at least one row ofstaples, said cartridge forming at least a portion of said secondinterfacing surface; an anvil for receiving and forming said staples,said anvil forming at least a portion of said first interfacing surface;electrically isolated first and second poles positioned on said firstinterfacing surface and comprising electrically opposite electrodes,wherein said first pole is comprised of first and second elongatedsubstantially parallel electrodes arranged on opposite sides of saidfirst slot and said second pole comprises an electrode positioned onsaid anvil; first and second compression ridges extending from saidfirst interfacing surface, wherein said first and second electrodescomprise at least a portion of said first and second compression ridges;third and fourth electrically insulating compression ridges extendingfrom said second interfacing surface; a first tissue contacting surfaceon said first and second compression ridges wherein said first tissuecontacting surface has a width of approximately 0.020 inches; a secondtissue contacting surface on said third and fourth compression ridgeswherein said second tissue contacting surface has a width ofapproximately 0.020 inches; and a recessed insulation region separatingsaid first pole from said second pole wherein said recessed insulationregion includes a recessed tissue contacting surface having a width ofapproximately 0.020 inches, said recessed tissue contacting surfacebeing approximately level with said portion of said first interfacingsurface comprising said anvil.
 5. The electrosurgical device of claim 4wherein said first and second electrodes comprise a series ofelectrically communicating electrode regions staggered on said firstinterfacing surface.